Public officials are generally shielded from lawsuits seeking damages for alleged wrongs resulting from official actions. But they are not protected from lawsuits when their actions violate someone's clearly established constitutional rights.

Under the 2001 Saucier decision, the high court required judges to follow a two-step procedure when assessing whether a particular official would enjoy the protections of qualified immunity. First, the judge must determine whether the facts as alleged in the case are a violation of a constitutional right.

Next, once the first step is satisfied, the judge must determine whether the right at issue was 'clearly established' at the time of the alleged misconduct.

If the answer to that question is yes, the official loses his or her qualified immunity.

That procedure was the law of the land until Wednesday, when the court announced that it was reconsidering the required sequence of the test.

"While the sequence set forth [in the Saucier decision] is often appropriate, it should no longer be regarded as mandatory," Justice Samuel Alito writes in the unanimous 20-page opinion.

"The judges of the district courts and the courts of appeals should be permitted to exercise their sound discretion in deciding which of the two prongs of the qualified immunity analysis should be addressed first in light of the circumstances in the particular case at hand," Justice Alito writes.

The decision arises in a case involving a lawsuit filed by a suspected drug dealer, Afton Callahan, against five state narcotics agents in Utah. Mr. Callahan sued the agents for allegedly violating his Fourth Amendment privacy rights by searching his house without a warrant.

In most law enforcement investigations, agents present evidence to a judge and obtain a search warrant that authorizes an intrusion into a person's home or business. In the Utah case the agents sought to rely on an exception to the warrant requirement. The exception allows police to search a home without a warrant if an undercover officer has already been granted permission to enter the home and has observed contraband in plain view.

The Utah agents sought to take this exception a bit further. Instead of an undercover officer, the agents relied on the presence of an undercover informant inside Callahan's trailer home to justify their search of the trailer without a court-ordered warrant.

Once the informant was in place, he signaled agents waiting outside. They entered the trailer where they found methamphetamine, marked bills from the informant, and drug syringes.

Prior to trial, Callahan's lawyer challenged the legality of the search. The Utah courts ruled that the agents acted improperly by not first obtaining a court-authorized warrant. The seized evidence could not be used against Callahan.

The suspected drug dealer then filed suit in federal court against the agents for allegedly violating his clearly established right not to have his home searched without a warrant. A federal judge threw Callahan's case out of court, but the Tenth US Circuit Court of Appeals reversed that action, ruling that the officers could be sued because they violated Callahan's "right to be free in one's home from unreasonable searches and seizures."

It is that decision that the Supreme Court reversed on Wednesday.

Writing for the court, Justice Alito said that at the time of the search, three federal appeals courts and two state supreme courts had considered similar warrantless searches and upheld them.

"Prior to the Tenth Circuit's decision in the present case, no court of appeals had issued a contrary decision," Alito writes.

"The principles of qualified immunity shield an officer from personal liability when an officer reasonably believes that his or her conduct complies with the law," Alito says. "Police officers are entitled to rely on existing lower court cases without facing personal liability for their actions."

Alito said that because it was not clearly established that the warrantless search technique the agents employed against Callahan was unconstitutional, the agents are entitled to the protection of qualified immunity.

Alito said the decision was aimed at giving greater flexibility to federal judges presiding over cases involving claims of qualified immunity. "Our decision does not prevent the lower courts from following the Saucier procedure," he writes. "It simply recognizes that those courts should have the discretion to decide whether that procedure is worthwhile in particular cases."